Page 328
REPAIR INSTRUCTIONS, PART 1
Rocker Arm and Engine Brake
Installation
[213 LP]
GENERAL INFORMATION
The rocker arms at the inlet valve locations are
identical for both non-brake and brake-equipped
engines. However, there are three exhaust rocker
arm designs used. The MACK PowerLeash™
engine brake uses a completely different exhaust
rocker arm design, while the non-brake and
J-Tech™-equipped engines use the same
design, but with different adjusting screw
arrangements:
앫 Non-brake engines use the internal hex
adjusting screw with jam nut.
앫 J-Tech™-equipped engines use adjusting
screws with spherical jam nuts at the
exhaust rocker arms.
In addition, J-Tech™-equipped engines use an oil
supply screw in place of the locating screw and
lock washer on the rocker arm mounting bracket.
This screw provides a passage for supplying oil to
the brake housing mounted on top of the rocker
arm. The screw also has an integral check valve,
eliminating the need for check valve components
in the engine brake housing.
The MACK PowerLeash™ engine brake uses a
completely different exhaust rocker arm design
with an integral brake piston. This design
incorporates a hydraulic actuator which
hydraulically locks to contact the inboard exhaust
valve.
INSTALLATION (NON-BRAKE EQUIPPED
ENGINES)
1. Make sure the locating screw and lock
washer are in position on the rocker arm
mounting bracket for each cylinder head.
2. Make sure that all 12 push rods are properly
seated in the respective lifter sockets with
standard push rods at the inlet valve
locations and spring-loaded at the exhaust
valve locations. Use care when checking the
push rod seating. DO NOT drop the push
rods onto the lifters.
Make sure the rocker adjusting screws are turned
completely upward into the rocker arms before
installing the rocker shaft or engine brake units on
the engine. If this is not done, tightening the
mounting bolts for the rocker shafts or engine
brake units, or rotating the engine to adjust the
valves, can bend the push rods or subject the
ceramic rollers to excessive loads which can
damage or break the rollers.
3. Place the rocker shaft assemblies in position
on the cylinder heads, making sure that the
mounting screw holes are properly aligned.
Depress the adjusting screw end of each
rocker arm so that the adjusting screw ball
end is down and in full contact with the push
rod cup. With the rocker arm depressed in
this fashion, rotate each push rod to be sure
it is properly seated in the lifter cup and at
the rocker arm adjusting screw.
If the rocker shaft assembly is lifted off the
cylinder head anytime during the installation
procedure, either partially or completely, steps 2
and 3 above must be repeated. Not having the
rockers properly positioned as described in
step 3, is the usual cause of a push rod being
dislodged from the lifter cup. If this should occur
and not be corrected, the ceramic roller will break
when the engine is rotated.
5-111.bk Page 328 Monday, July 10, 2006 2:26 PM
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